The term "ultrasonic radiation" is employed in this specification to designate pressure-rarefaction waves differing from sound waves in exhibiting higher frequencies and shorter wavelengths. The term "ultrasonic exposure" is employed to designate exposure to ultrasonic radiation. The production of visible images by means of ultrasonic radiation is referred to as "ultrasonoscopy". The production of a visible record by means of ultrasonic radiation is referred to as "ultrasonography". The instruments for producing ultrasonoscopic images are designated "ultrasonoscopes", and the ultrasonoscopes which produce ultrasonographic images are referred to as "sonographic cameras". The definition of terms as here presented is believed to be generally consistent with the use of these terms in the art. Specifically, these terms are suggested by P. J. Ernst in the Journal of the Accoustical Society of America, Vol. 22, No. 1, in an article entitled "Ultrasonography", pp. 80-83, January 1951.
The prior state of the art with respect to the action of ultrasound on silver halide photographic elements is reviewed by M. E. Arkhangel'skii, Soviet Physics-Acoustics, Vol. 12, No. 3, "Action of Ultrasound on the Processes of Photographic Development and Fixing", pp. 241-248, January-March 1967. The ability of ultrasound exposure to produce a latent image in silver halide emulsions has been recognized since the 1930's. However, power level requirements to achieve ultrasonic imaging have been quite high, and there have been controversies as to whether the ultrasound directly produces the latent image or stimulates other effects, such as cavitation-stimulated luminesence, which produces the latent image. It has been a difficulty in the art that ultrasonic exposure requirements of silver halide photographic elements, even with the most responsive techniques known to Arkhangel'skii, have remained unattractively high. For example, such techniques have required intensity and time levels of ultrasonic exposure which are objectionable to many non-destructive testing applications, such as mammographic examination with ultrasound as described by Brendon U.S. Pat. No. 3,765,403.
Rosenfeld U.S. Ser. No. 854,556, filed Nov. 25, 1977, titled AN IMPROVEMENT IN ULTRASONOGRAPHY, now abandoned in favor of copending U.S. Ser. No. 031,083, filed Apr. 18, 1979, now U.S. Pat. No. 4,223,082 is directed to an improved process of ultrasonic imaging in which a visible ultrasonic image is formed in a silver halide element by imagewise exposing the element to ultrasonic radiation, thereby altering its photographic response, and concurrently or subsequently exposing the silver halide element to electromagnetic radiation to form a developable latent image. The element is then photographically processed to produce a visible image corresponding to the latent image. In an ultrasonographically negative-working form Rosenfeld brings into contact with a transport liquid an element containing a silver halide emulsion layer which is initially desensitized to light by the presence of an incorporated diffusible ion. The element is imagewise exposed to ultrasound. This has the effect of locally sensitizing the emulsion to light, so that upon light exposure and photographic processing a maximum density is produced in areas of the element which are ultrasonically exposed. In an ultrasonographically positive-working form the silver halide emulsion is initially sensitive to light and is brought into contact with a transport liquid containing diffusible ions capable of desensitizing the emulsion to light. Imagewise ultrasonic exposure results in local desensitization of the emulsion to light, so that light exposure followed by photographic processing produces a minimum density in areas of the element which are ultrasonically exposed. In one variant form both a polar solvent and a diffusible densensitizing ion are initially incorporated within the silver halide emulsion. In other variant forms the diffusible ion has the effect of sensitizing the silver halide emulsion. The disclosure of Rosenfeld is here incorporated by reference.